Recovery of oil by strip-mining



p attaass Patented Oct. 22, 1963 This is a continuation-in-part of application Serial No. 760,935, filed on September 15, 1958.

This invention relates to a novel method for separating and recovering oil from open pit, mined formations. It particularly pertains to methods for recovering oil by means of an aqueous surfactant solution, and is especially significant because it also provides for the reclamation and re-use of the surfactant.

Broadly stated, the object of my invention is to provide an eflicient method for effecting the recovery of oil by strip-mining operations in which an aqueous surfactant solution is employed to accomplish the oil recovery, and for recovering and re-using most of the surfactant so used.

Another object is to provide a process for the recovery of oil by the use of an aqueous surfactant solution which causes an oil-Water emulsion to be produced, said emul sion being readily and inexpensively broken so that the surfactant can be efficiently recovered in a single phase and re-used and the oils economically obtained.

Other objects of the invention, together with some of the advantageous features thereof, will appear from the following description and specification. In most cases, recovery of the surfactant will be a principal feature; however, the invention is not necessarily limited thereto as in certain applications it will be useful only to emulsify and demulsify in accordance with the novel methods herein described.

Many agents have been proposed for emulsifying and demulsifying oils. But in certain applications, notably in the recovery of oil from various unusual petroleumbearing formations, such as tar sands, these agents have proven unsatisfactory for one reason or another. Among the principal objections are the use of relatively costly emulsifying materials which are substantially non-recoverable, the difficulty in forming the emulsions, the difficulty in breaking the emulsions, etc.

The present invention overcomes all of these objections by the novel use of certain surfactants in emulsificationdemulsification procedures which make possible high recovery of all components by controllably changing the hydrophile-lipophile balance of a surfactant during the process. (The terms surfactant and emulsifier or emulsifying agent as hereinafter employed may be used interchangeably.) The controlled change of this balance is brought about by the use of pH-sensitive emulsifiers: The oil is either emulsified under alkaline conditions and the emulsion later broken by adding acid to make the solution acidic, or emulsified under acid conditions and broken by adding alkali to make the solution alkaline. In actual practice, it may be desirable in some cases to effect a closer control of the acidity or alkalinity of the treated solution in order to maximize the recovery of surfactant. This variation of pH effectively controls emulsion stability and the concentration of the surface-active agent in each phase.

In my process, when stability of the emulsion is renderecl a minimum, recovery of the surfactant for re-use is facilitated either by preferential solubility of the slitfactant in the organic or the aqueous phase or by precipitation of the surfactant. My invention may thus be practiced in three alternative procedures which may conven iently be grouped as follows:

CATEGORY A (1) Make oil-water emulsion by means of a surfactant (2) Recover surfactant in aqueous phase by suitable control of pH in both steps CATEGORY B (1) Make oil-water emulsion by means of a surfactant (2) Recover surfactant in organic phase by suitable control of pH in both steps CATEGORY C (1) Make oil-water emulsion by means of a surfactant (2) Recover surfactant as a precipitate by suitable control of pH in both steps As indicated earlier, and as will be explained in more detail below, the emulsions formed in each of the above categories may optionally be made in a base and broken with an acid, or vice versa.

Ordinarily, in emulsions, appreciable fractions of the total emulsifier are found in three locations: (1) the bulk oil phase; (2) the bulk aqueous phase; and (3) in the region of the interface. In my invention, I not only destroy the emulsion, but also effect a concentration of the surfactant in one bulk phase or the other as I choose. This choice is made dependent on the contemplated mode of re-use of the surfactant or of the surfactant solution. In some cases, I may choose to concentrate a surfactant as a separate, pure-or almost purephase for convenience in re-use. This ability to concentrate, in one phase, a good emulsifier which otherwise isspread. .QYQIlllI locations as above explained, is a novel as well as highly useful feature of my invention.

Examples of Process Employing Single Cycle Not all surfactants will work in my novel process and, of those that do work, not all of them will function satisfactorily in each of the three categories described above. The selection and manner of employment of the various surfactants are, therefore, important to the successful practice of the invention. In essence, it may be stated that any surface having Weakly acidic or weakly basic groups will Work in one or more of the systems encompassed by my invention. The surfactants which will not work efficiently are those whose hydrophilic portion is entirely (a) non-ionic, or (b) composed of the anion of a strong acid or of the cation of a strong base.

In the numerous examples which were conducted to demonstrate the operation of the invention, the starting solutions employed were divided into two main sets. One set was a 0.5 percent solution of the surfactant in 0.5 percent NaOH, and the other set was a 0.5 percent solution of the surfactant in 0.5 percent H 50 However, in order to demonstrate effectiveness at different concentrations, several experiments were run in which the initial surfactant concentration ranged from 0.05 to 20 percent.

Equal volumes of the oil and of the surfactant caustic or of the surfactant-acid solution (as the case may be) were placed in each of two screw-cap jars and agitated on a reciprocating type shaker for 15 minutes. The emulsified contents Off one jar were poured into a graduated cylinder and allowed to stand for one hour, at which time the volumes of the various phases were recorded and the percent recovery of the aqueous phase (a measure of emulsion instability) computed. To the contents of the. other jar either acid or base was added until the pH was rendered below about 5 in the ones which were made acidic and above around 9 in the ones which were made alkaline. the emulsion, or after one hour, whichever was earlier, the volumes of the organic and aqueous phases, respectively, were; recorded. Suitable surfactants for :the particular oil-water system gave low instability in the first jar and high instability in the second jar. The emulsion instability one hour after adding the acid or base was computed and reported as the percent recovery of the aqueous phase. a

For any surfactant having weakly acidic or weakly basic groups, oil-Water systems will be found in which my invention will operate efficiently. Conversely, for any given oil-water system, surfactants of this type exist which will work efiiciently. It is well known in the art that the hydrophile-lipophile balance of an emulsifier determines its effectiveness for a given oil-water system. Thus, the 2 well known techniques for choosing a good emulsifier are to be applied to the classes containing weakly acidic or weakly basic groups as a preliminary step in the practice of my invention. This was done as described in the following paragraphs.

All the tests were conducted at room temperature. The pH was checked at two or more points in each case. The surfactants which formed a. relatively stable emulsion in base were deemed to be useful in the processes of all three categories, A, B, and C, previously described, particularly the processes in which the oil was emulsified in Afiter complete breaking of 10 4, 7 base and broken with acid. High, low, or moderate recovery of the surfactant in the aqueous phase determined whether the surfactant belonged in category A or B or failed to qualify. If a high percentage of the surfactant precipitated upon acidification, the surfactant qualified for category C. The same principles were used in determining the utility of surfactants for the processes in each of the three categories in which the oil was emulsified in acid and broken with base, except that the direction along the pH scale was reversed.

The above-described tests involved a single cycle proc ess, and the data obtained thereby are represented in Tables 1, 2, 3, and 4. Other experiments were run with a recycling process, which will be described in detail be low, and the data obtained thereby are represented in Tables 5, 6, and 7. In almost all of the examples, the oils used were toluene and Ventura crude oil (a relatively clean crude oil). Six other oils (i.e., organic liquids which are insoluble in water) were used to test the efficiency of the invention under various conditions making a total of eight as follows:

TABLE IEEMULSIFIED IN CAUSTIO, BROKEN WITH ACID; SURFACTANT RECOVERED IN AQUEOUS PHASE [Organic phase: Toluene. Aqueous phase: Surfactant, 05% NaOH, deionized H20 (all pHs: 12.813.1)]

Surfactant Mole ratio cone. in Emulsion pH 0 after Emulsion A-perccnt Bpercent Surfactant of E0 weight/ instability acidifiinstability of I. O. of of I. C. of A+B d (n) a volume in caustic cation after acidsurfactant surfactant percent; ification in aqueous in toluene (I. C.) b

10. 0 0. 5 V 36 3-4 102 98 3 101 12. 6 0. 5 35 102 15.0 0.05 98 6 7 15. O 0.5 22 2-3 100 100 1 100 15. O 5. 0 18 4 101 89 O 89 20.0 0. 5 32 2.1 101 98 1 99 20.0 20.0 0 1. 5 103 101 1 102 30.0 0, 5 30 2-5 103 101 3 104 3 0. 5 61 4 101 78 42 15 0. 5 61 3. 0 101 96 2 98 20 0.5 14 2. 8 71 94 2 96 .NOTES ON TABLE 1 (1) Surfactants Nos. 1-8 were ethylene oxide adducts of a commercial product comprising a mixture of amines which principals covers the range of CnHgaNHz t0 CwHaaNHz, the number of ethylene oxide units per amine being from 10 to (2) Surfactants Nos. 9-10 were ea referred to in note (1) above.

oh the sodium salt of the sulfated ethylene oxide adducts of the type (3) Surfactant No. 11 was a commercially available'product, a dehydroabietylamine ethylene oxide adduct with the structure in which z+y=20I n=numbcr of units of ethylene oxide, including the ethanol termination, in the polycther chain. b I.O.=i nitial concentration of surfactant expressed as weight/volume percent. a A single result such as 3 or 3. 0 denotes that all of the data were taken for this one pair of emulsions. Where V a range is indicated, such as 2-4, one of them (the 2 or the 4) was a repeat. The figures not reported to a tenth of a pH unit were determined by using pH test papers; the other figures were obtained with a pH meter.

d A+B should equal 100 percent for complete accountability of the surfactant.

0 Result obtained'was greater th concentration of the surfactant.

an 100 percent due to limitations of method of analysis caused by the low 6 Whereas Table 1 contains data comparing various surin which only toluene was employed, Table 2 which folfa'ctants used in an emulsification-demulsification system lows compared surfactants inthe process as applied to various other oils.

TABLE 2.EMULSIFIED IN CAUSTIC, BROKEN WITH ACID; SURFACTANT RECOVERED IN AQUEOUS PHASE [Organic phase: Various oils listed. Aqueous phase: Surfactant, 0.5% NaOH, deionized H2O] Surfactant Emulsion cone. in Emulsion pH after instability Percent of Surfac- Mole ratio weight] Oil used instability acidificaafter LC. of

taut of 110(11) volume in caustic tion aeidificasurfactant percent tion in aqueous (1.0.) b

12. 6 0. 5 Ventura crude oil 56 6. 6 90 15.0 0.05 do 4 3 4 96 15. 0. 5 44 3. 4 98 99 15. O 5. 0 8 3. O 100 93 20.0 0.5 40 4 0-4. 5 101 20. 0 20.0 0 1. 4 95 99 30. O 0. 5 40 2. 4-4 100 r 0. 5 22 4. 0 75 15 0. 5 54 2. 6 100 25 0.5 62 V 2. 5 96 15 0. 5 44 2. 9 100 0. 5 -70 2 93 20 0. 5 46 2. 6 98 15 0. 5 59 2 3 99 96 15 0. 5 Hawk. Field 53 2 3 97 89 20 0. 5 Wesson oil 79 2 20 5.0 do 50 2 94 98 20 0. 5 Mixture of lauryl and 0 2. 1 0-32 myristyl alcohols.

NOTES ON TABLE 2 (1) Surfactants Nos. 1-7 and 14-17 were the same as described in note (1) in Table 1.

(2) Surfactant No. 8 was the same as described in note (2) in Table 1.

(3) Surfactants Nos. 9-10 were ethylene oxide adducts of a mixture of amines which principally covers the range of C172-lI'I35-4DNH2 where the number of ethylene oxide units per amine is 15 and 25, respectively.

(4) Surfactants Nos. 11-12 were a coco-amine ethylene oxide adduct, and a stearyl-amine ethylene oxide adduct, respectively. The formers structure is in which x+y=15; the latter has the same structure except that z+1 =50.

(5) Surfactant No. 13 was a commercially available product, a dehydroabietylamine ethylene oxide adduet with the structure (0 11201320) 3H R-N (GHaCHzO) yH in which x+y=20.

(6) Surfactant No. 18 was sodium p-t-octylphenoxypoiyethoxy (20 units) acetate with the structure RO(CH;OH-;O) oCHzCOONE.

B Same as footnote a in Table 1. b Same as footnote b in Table 1. c Same as footnote 0 in Table 1. t The Venture crude oil contains some impurities which were extracted into the aqueous phase in some ins ances.

e Same as footnote e in Table 1.

TABLE 3.EMULSIFIED 1N CAUSTIC, BROKEN W'ITH ACID; SURFACTANT RECOVERED ASPRECIPITATE [Organic phase: Toluene (except for item marked by asterisk in which Ventura crude oil was used). Aqueous phase: 0.5% surfactant, 0.5% NaOH, deionized water] NOTES ON TABLE 3 (1) Surfactant N0. 1 was disodium B-tallow iminodipropionate. (2) Surfactant N0. 2 was disodium B-lauryl iminodipropionatc. (3) Surfactants Nos. 3 and 4 were sodium fl-coco amino-propionate.

= Same as footnote a in Table 1. b Same as footnote d in Table 2.

TABLE 4.EMULSIFIED IN ACID. BROKEN wr'rn BASE; sURFAo'rAN'r RECOVERED IN AQUEOUS on ,ORGANIO PHASES [Organic phase: Toluene (except for items marked by asterisk in which Ventura crude oil was used). Aqueous phase: 0.5% surfactant, 0.5% H 80 deionized water (all pHs: 12)]' NOTES ON TABLE 4 (1) The results with surfactants 1-6 inclusive show the difierent effects with different oils. Note that with \lentura crude the same surfactant that worked well in Nos. 2 and 4 did not work at all with toluene 111 Nos. 1 and 3. Similarly, with Venture crude in No. 6, a good result was obtained, but in No. 5 toluene did not work at all.

(2) Surfactants Nos. 1-6 were the same as described in note (1) in Table 1. (3) Surfactants Nos. 7 and 8 were the same as described in note (6) in Table 2. (4) Surfactant No. 9 was sodium N-polyethoxy (11 units) ethyldodccenylsuccinamate.

e Same as footnote a in Tablel.

In the examples shown in Tables 1 to 4, the number Examples of Process Employing Continuous Cycles From the foregoing tables, it was apparent that among the surfactants which may be employed in the inventive process, one of the most successful types is the group comprising a number of amine-ethylene oxide adducts. Of these, the products, identified as an ethylene oxide adduct (15-30 units) of a commercial product comprising a mixture of amines which principally covers the range t-C H NH to t-C H NH excelled all other surfactants tested in several oil-water systems when consideration was given to emulsion stabilityin caustic solution, efiiciency (time and completeness) of breaking, and recoverability of the surfactants. One of them (the one having 15 units of ethylene oxide) was therefore selected for a series of recycling experiments inwhich the same batch of causticsurfaotant solution was used repeatedly to 'form the emulsion, then reclaimed, freed of most of the inorganicsalt, and used again to emnlsify a fresh batch of the same oil. The number of cycles in each experiment was limited only by the fact that the volume of emulsion was constantly being decreased as samples-were removed for determination of emulsion stability in caustic solution and for analysis. This type of limitation will vary, depending upon the scale on which my invention is practiced, any samples needed during the process, etc., if no make-up surfactant is used.

The results obtained with the recycling process are set forth in Tables 5-8. They were obtained by the following procedure: r

Equal volume of oil and of'a 0.5 percent caustic 0.5 percent surfactant solution (500 cc. of each phase at the start) were vigorously mixed by a mechanical shaker for 15 minutes. A control sample of the emulsion waswithdrawn for measuring emulsion stability in caustic, allowed to stand for an hour, and the phase volumes read. The remaining emulsion was poured into a graduated separatory funnel and dilute H 50 added until the emulsion broke and the pH was below 5, shaking well after adding each increment. The completeness of breaking (i.e., percent recovery of oil) was determined.

A sample of the aqueous phase (and of the organic phase in the case of toluene) was withdrawn and analyzed for surfactant. An amount of Ca(OH) equivalent to the H present was added to the solution. The solution was shaken for a few minutes, then filtered to remove the precipitate. A sufiicient amount of NaOH was then added to raise the pH to that of the starting solution, viz., 12.8-12.9.

Failure to remove CaSO prior to replenishing caustic would result in the redissolving of some CaSO and such removal is therefore preferable. (If other alkaline materials are used in lieu of the Ca(OH) the problem need not occur. Optionally, also, HCl [or any other inorganic acid, or organic acid or acid salts] could be used instead of H 80 and other alkaline materials can also be used. The HCl and NaOH will form NaCl which can be allowed to accumulate or may be removed by some other means without interfering with the process.) The Ca(OH) precipitated by the NaOH was eliminated by refiltration. The volume of the filtrate was measured and an equal volume of fresh oil added thereto, after which all ofthe foregoing steps were repeated a number of times as shown in Tables 5-8.

The cyclic process is typically represented in the diagram shown in the attached drawing which illustrates an application of my invention to oil recovery from petroleumbearing formations. The drawing shows my novel process as applied to oil recovery via the strip-mining techniques.

Tables 5.8 set forth data obtained when the cyclic process was applied to each of four difierent oils, using one of the preferred surfactants (the one having 15 units of ethylene oxide as an adduct of t-C H NH as aforesaid.

TABLE 5.TOLUENE V Emul. Oumu- Cum. Emul. pH lnstah. Percent lative Percent Percent Cycle instab. after after 0 Percent of LC. of No. in acidifiaoidifi- LC. of in LG.

control cation cation in H2O 1.0. tol. iri to LC. is initial concentration.

= LC. is initial concentration. I

TABLE 7.HOWARD GLASSCOOK CRUDE OIL Emul. pH after Emul Percent of Cumula- Cycle Instab. in acidificn- Instab .Cs in ative per- No. in control tion after ucidi H O cent of 1.0.

fication LC. is initial concentration.

TABLE '8.H.&WEINS FIELD CRUDE OIL Emul. pH after Emul. Percent of Cumula- Cycle Instab. in acidifica- Instab. 1.0. in ative per- No. in control tion after acidi- H O cent of 1.0,

fication LC. is initial concentration.

Some of the more salient points reflected by the recycling data in Tables 5-8 may be summarized as follows:

Average Percent Recovery of Aqueous Phase After water-imoil emulsion could not be determined.

Average Percent Recovery of Surfactant Into Aqueous Phase Toluene 100 Ventura 94 Glassoock 94 Hawkins 91 Conclusions and Observations The foregoing description has clearly demonstrated the eflicient manner in which my invention can be employed in connection with the recovery of oil by such common practices as the strip-mining type of operation. The oil is emulsified with an emulsifying agent, then the 16 emulsion is broken, and the emulsifier is recovered and is available for re-use. This is done by either adding to the oil a base in a surfactant solution, and breaking the emulsion by adding acid, or by adding acid in a surfactant solution and breaking the emulsion by adding a base.

I claim:

1. In an oil recovery process in which mined oil-bearing formations are treated in a reservoir such as an open pit, the steps which comprise agitating portions of the mined formations with an alkaline aqueous solution of a pH-sensitive surfactant so as to emulsify the oil in the mixed formations, the surfactant being selected from the class consisting of (a) the ethylene oxide adducts of a range of amines represented by the formula C ,,H NH where the number of ethylene oxide units is from 5 to 50 per amine;

C11 24H23 49NH(C2H4O)HSOANH, Where 11:3 to

and

in which R is a dehydroabietyl group and x+y=15 to 50, mowing the solids to settle, and subsequently breaking the emulsion by addition of an acidic substance so as to make the oil-water system acidic and thereby concentrate the surfactant in a bulk phase where it is available for further use, while concentrating the oil in another phase.

2. In an oil recovery process in which mined oil-bearing formations are treated in a reservoir such as an open pit, the steps which comprise agitating portions of the mined formations with an acidic aqueous solution of a pH-sensitive surfactant so "as to emulsify the oil in the mixed formations, the surfactant being selected from the class consisting of (a) the ethylene oxide adducts of a range of amines represented by the formula C H NH where the number of ethylene oxide units is from 5 to 50 per amine;

C H NH(C H O) SQgNa, Whore "=3 to 5 and (C 2114 YH in which R is a dehydroabietyl group and x+y= 15 to 50, allowing the solids to settle, and subsequently breaking the emulsion by addition of an alkaline substance so as to make the oil-water system alkaline and thereby concentrate the surfactant in 'a bulk phase where it is available for further use, while concentrating the oil in another phase.

References Cited in the file of this patent UNITED STATES PATENTS 1,615,121 Fyleman Jan. 18, 1927 1,925,551 Wietzel et a1 Sept. 5, 1933 2,654,676 Dryden Oct. 6, 1953 2,662,062 Sumerford Dec. 8, 1953 2,719,118 Bernard et a1 Sept. 27, 1955 2,784,161 Foley Mar. 5, 1957 2,825,677 Oonlson Mar. 4, 1958 2,910,424 Tek et a1. Oct. 27, 1959 OTHER REFERENCES The Chemistry of the Fatty Amines, published by Armour and 00., 1948, pp. 1-5, 17 and 18. 

1. IN AN OIL RECOVERY PROCESS IN WHICH MINED OIL-BEARING FORMATIONS ARE TREATED IN A RESERBOIR SUCH AS AN OPEN PIT, THE STEPS WHICH COMPRISE AGITATING PORTIONS OF THE MINED FORMATIONS WITH AN ALKALINE AQUEOUS SOLUTION OF A PH-SENSITIVE SURFACTANT SO AS TO EMULSIFY THE OIL IN THE MIXED FORMATIONS, THE SURFACTANT BEING SELECTED FROM THE CLASS CONSISTING OF (A) THE ETHYLENE OXIDE ADDUCTS OF A RANGE OF AMINES REPRESENTED BY THE FORMULA C11-24H23-49NH2 WHERE THE NUMBER OF ETHYLENE OXIDE UNITS IS FROM 5 TO 50 PER AMINE; (B) C11-25H23-49NH(C2H4O)NSO4NA, WHERE N=3 TO 50; AND 